1. Field
The present invention relates to a cooling unit of liquid cooling type that uses a radiator to cool a heat generating component (e.g., CPU) with liquid coolant. The invention relates also to an electronic apparatus such as a portable computer, which incorporates the cooling unit.
2. Description of the Related Art
A CPU is incorporated in electronic apparatuses such as portable computers. The heat that a CPU generates while operating is increasing as its data-processing speed rises or as it performs more and more functions. The higher the temperature of the CPU, the less efficiently it operates or the more likely it may fail to operate.
To cool the CPU at high efficiency, cooling systems of so-called “liquid cooling type” have been put to use in recent years. The cooling system uses a liquid coolant whose specific heat is far higher than that of air, in order to cool the CPU.
The conventional cooling system has a heat receiving portion, a heat radiating portion, a coolant passage, and a fan. The heat receiving portion receives heat from a CPU. The heat radiating portion radiates the heat generated by the CPU. The coolant passage is filled with liquid coolant that transfers heat from the heat-receiving portion to the heat-radiating portion. The fan applies cooling air to the heat radiating portion.
The heat radiating portion has a pipe and a plurality of heat-radiating fins. The liquid coolant heated by virtue of heat exchange at the heat-receiving portion flows through the pipe. The heat-radiating fins are arranged in a row, spaced apart from one another. The pipe penetrates the center parts of the heat-radiating fins. It is thermally connected at its outer circumferential surface to the heat-radiating fins, by means of, for example, soldering or the like.
The fan comprises a fan case and an impeller provided in the fan case. The fan case has an outlet port, through which cooling air is discharged. The outlet port opens to the heat radiating portion. The cooling air discharged through the outlet port passes through the gaps between the heat-radiating fins. The cooling air takes away the heat transferred from the liquid coolant via the pipe to heat-radiating fins. The liquid coolant heated at the heat radiating portion is therefore cooled as it exchanges heat with the cooling air. Jpn. Pat. Appln. KOKAI Publications 2003-101272 and 2003-258472, for example, disclose electronic apparatuses that incorporate a cooling unit that has such a heat radiating portion and such a fan.
In the cooling units disclosed in these publications, the heat radiating portion is positioned outside the fan case. The shape of the outlet port of the fan case inevitably limits the size of the heat radiating portion and the number of heat-radiating fins. As a result, the heat radiating portion cannot have a sufficient heat-radiating area. Consequently, the heat radiating portion cannot efficiently radiate the heat generated by the CPU and absorbed into the liquid coolant.